MORE ON:

David Stuart MacLean woke up one day in October 2002 in a disturbing manner, as he suddenly came to consciousness standing on a train platform in India. “It wasn’t a gradual waking process,” he writes. “It was darkness darkness darkness, then snap.”

Standing in the center of a crowd, he had no idea who he was or how he had gotten there.

“I could feel a heavy absence in my brain, like a static cloud,” he writes. “I couldn’t remember anything past waking up. There was a thick mass of nothing up there. I was alone with no idea how far I was [from] anyone who knew me. I was alone and empty and terrified. I wiped my face with both palms. I blacked out.”

In ways he couldn’t have imagined at the time, his life would never be the same.

“The Answer to the Riddle Is Me” (Houghton Mifflin Harcourt) is a highly affecting memoir about the most literal sort of identity theft, as MacLean, then 28, found that his entire life — his family, his friends, his loves, his passions, every aspect of himself from his name and history to the kind of person he was — had been erased from his mind.

Shortly after MacLean came to on the platform, he found a “tourist police officer” staring down at him. To his amazing luck, the first person to find him — to outside eyes, a collapsed, probably drugged-out, immensely vulnerable tourist — was honest and well-intentioned.

“I am here for you,” the officer told him. “I have seen this many times before. You foreigners come to my country and do your drugs and get confused. It will be all right, my friend.”

With only this info to go on, MacLean filled in the details of his life. He was, clearly, a dangerous drug addict.

“I was relieved. I should have known,” he writes. “This was the kind of trouble drug addicts ended up in all the time. It was serious, but I was thankful that this police officer had let me know who I was and that I wasn’t to be trusted.”

With that, scant memories began filtering back. He recalled “doing drugs with an unattractive redhead in a dark apartment. Her ginger face was covered in acne and nickel-sized freckles. Images of her coming toward me twirling little baggies full of toxic stuff flickered in my brain. Cooking. Injecting. Snorting. Scoring. This is what drug addicts do.” He later remembered that her name was Christina.

The officer, Rajesh, who went by “Josh” for Americans, later dictated an e-mail for him to write to his parents — MacLean had his wallet with him, so they were able to determine his name — letting them know he was in trouble in India, but that he would be OK. In the e-mail, Josh had him promise to “endeavor to earn your respect back,” and to apologize that “I ever touched these drugs.”

Josh then brought him to the home of a woman, Mrs. Lee, who gave overdosed tourists a place to recuperate. Her own son had died after being dosed with drugs in a foreign country, and when she told MacLean her story, he was overcome with guilt and started bawling.

“It was people like me who killed her son,” he writes. “I put my hand on hers and told her I was sorry, that I’d do better, that I was done with all of the drugs. Forever.”

But MacLean would soon realize that being an amnesiac drug addict was only part of his problem. Other psychological disturbances were settling in as well, as he learned when he laid his head down to sleep.

“The room began to twist,” he writes. “One corner of the ceiling would be pulled down and nearly brushing my lips and the other would be stretched out miles away. Then the corners would swap distances. Floating clouds of color spun and drifted throughout the room. Sometimes one of those clouds would come and sit squarely on my chest, driving all my oxygen out. The little stool in the corner of the room clattered and moved as soon as I stopped watching it. I’d catch it doing pirouettes in my periphery.”

MacLean wound up in a local mental hospital, where he spent three days falling in and out of consciousness, driven by further hallucinations. He had a revolving door of visitors he couldn’t identify, but who seemed to know him quite well. He hallucinated that one visitor, who resembled Jim Henson, was God, taking him on a floating tour of the universe.

In the midst of these visions, there was still the matter of his debauchery. He was certain that at any moment, Christina would be hauled in, arms cuffed behind her back, forcing MacLean to account for the horrible things he’d done.

“When I finally got better, they’d reveal my catalog of crimes and convict me,” he writes. “I just had to get well enough to handle my guilt.”

But MacLean was not a drug addict, he had committed no crimes, and Christina did not exist.

What MacLean — in actuality, an American writer in India on a Fulbright scholarship to research Indian dialects for a novel — came to learn, as his frantically worried parents flew to India to bring him home, was that the most likely culprit was the anti-malarial drug Lariam, a drug with a history of frightening side effects that had nevertheless been regularly issued to our soldiers overseas.

The malaria drug, Lariam

MacLean includes much of the drug’s history in the book, and the prospect of having to take it is enough to make you never want to travel overseas ever again.

“As soon as Lariam was made available, reports of extreme behavior started popping up,” he writes. “In 1992, a Canadian soldier in Somalia savagely beat a civilian to death and then attempted suicide in a holding cell, resulting in permanent brain damage. The Canadian soldiers in this unit referred to the day they were supposed to take their weekly dose of Lariam as ‘Psycho Tuesdays.’ ”

But that’s nothing compared to the effect it had on our own soldiers. Two UPI reporters, Mark Benjamin and Dan Olmsted, reported on the drug at length from 2002-04. Among other things, including citing “mounting evidence” that Lariam caused suicides, they implied a connection between Lariam and several brutal cases in 2002 where Special Forces soldiers at Fort Bragg each murdered their wives and then themselves.

(In 2012, an Army epidemiologist testified before a Senate committee that Lariam was “the Agent Orange of our generation.” And yet, as of spring 2012, MacLean writes, the drug was “still being given to US soldiers stationed in sections of Afghanistan.”)

As he learned more about Lariam and pieces of his memory began to filter back, MacLean remembered that this was not his first experience with the drug, as he had taken it once a week in 1998 while on a months-long, post-college trip to India.

At one point during the trip, he arranged to stay at a private boarding house run by a woman and her son.

During his first night there, he went for a bike ride. On his way back, he rode through a rubber-tree forest, and the trees took on a menacing air. “I stopped, folded over, gasping for breath — and I felt something in the forest, something with teeth, that was looking for me.”

When he returned to the house, he went into the kitchen, where the woman sat, and took particular notice of her knives.

“I knew where the knives were. We were alone. I could kill her,” he thought. “I could see her dead already in my mind.”

He brought himself under control by sticking a pen a full quarter of an inch under his thumbnail until the “excruciating” pain distracted him, bringing tears to his eyes. He continued this throughout the night, and left the house the following morning.

“I had never had homicidal thoughts in my life before that night,” he writes. “I told myself it was because I had been alone so long. I figured the Lariam had something to do with it, but only because it gave me such crazy dreams. I felt terrible; I was ashamed that my brain could produce such things.”

Back in the States, MacLean began to receive calls and e-mails from concerned friends. They knew him intimately. He didn’t know them at all. His parents filled in many of the blanks. In India, his mother had mentioned to him that Anne and Sally were very excited to see him. It was some time later that he finally learned that Anne and Sally were his girlfriend and his dog.

He poured over photo albums and old e-mails, desperate to fill in blanks. Hallucinations and panic attacks subsided, then returned. Elements of his past filtered through as scant images, with occasional exceptions — song lyrics often came to him whole — but rarely enough to fill his memory gaps with any significant information about his life.

When he spoke to Anne on the phone for the first time, he found her voice “faintly familiar, like the smell of the car heater the first time you turn it on in the fall,” but he “could not remember anything about our relationship.” (After faking his way through a weekend with her that included his waking one night in the midst of a massive hallucination, he broke off the relationship.)

In time, MacLean would hold his reunions the way a spy holds meetings.

“I let the other person lead the conversation, and I agreed with whatever was said, adding bland rejoinders, if necessary,” he writes.

Another complication emerged as well. As he learned who the old David MacLean had been, he was taken with the realization that he may not be a person worth re-becoming.

As he e-mailed friends about his extraordinary ordeal, he found the responses disbelieving, with many assuming he was playing a prank, including those he’d just met in the Fulbright program.

Of a response from one woman who replied, “. . . if you’re making this up, you are a big jerk,” he writes, “I could only have known this woman for a maximum of two months, yet she knew that I was capable of creating fabrications and passing them off as truth.”

Later, at a drunken party, a female acquaintance who had known him since before the incident blurted out to him, “You don’t respect women.” When he later asked his mother about this, she replied, “The real problem with her statement is that it makes it seem like you respect men.”

While he has only flickers of his old life in his head, MacLean, who suffered seizures as late as 2007, has managed to build a new life from the ashes of the old, including marrying and having a child.

In the end, he’s done his best — as the existence of this book indicates — to come to terms with his ordeal and not allow it to halt his life.

He writes at one point how quickly he is “to point out how unlucky I am,” given that, “though studies . . . say that 25% of people who take [Lariam] have adverse psychological side effects, only a slim minority of that percentage reacts to the drug like I did.

“When my mom tells my story,” he writes, “she always points out how lucky I am to have made it through alive.”